Fault-Tolerant Function of DC-Bus Power Source in A Dual Inverter Drive System and Its Operation Characteristics

Abstract

The dual inverter drive system feeding an open-end winding permanent magnet (PM) motor has been studied for developing autopilot technologies of hybrid vehicles. Autopilot systems require fault-tolerant functions, which enable it to continue to drive the motor even if some failure occurs in the motor drive system. The fault-tolerant function of a dual inverter drive system, which assumes that the DC-bus battery power source of the dual inverter drive system has failed, is discussed in this paper. In the dual inverter drive system that is considered, both the inverters have a capacitor in parallel with a battery across each DC-bus. The capacitor drives the motor continuously even if the DC-bus battery has failed. The inverter, in which the DC-bus battery has failed, is operated with the capacitor instead of the failed battery. It is required to both control the capacitor voltage at a constant value and simultaneously generate multilevel voltage waveforms across the motor windings with the space vector modulation (SVM). In this paper, the fault-tolerant function of the DC-bus battery in a dual inverter drive system is proposed, and its operation characteristics are examined through several experiments and compared with those of a normal system.

Experimental Verification of Fault Tolerant Operation Focusing on DC-Bus Battery Failure in Dual Inverter Motor Drive

“…However, the fault tolerant operation of the DC-bus battery has not been considered in detail [16,17]. Therefore, the authors have focused on a redundancy in the switching states of the dual inverter motor drive and have studied the fault tolerant operation of the DC-bus battery [18,19]. In the studied operation, the failed battery is isolated with a relay, after some failure it is detected through the battery management system.…”

“…Figure 3 shows the output voltage vectors and the switching states of the dual inverter motor drive from 0 to 60 degrees, where the capacitor charging and the discharging modes are also described. As shown in Figure 3 and described in Reference [19], the 1:0.5 DC-bus voltage ratio is employed and the capacitor voltage of the INV2 is controlled at half of the battery voltage of the INV1 in the fault situation, because it cannot switch over the charging mode and discharging mode redundantly in the case of the 1:1 DC-bus voltage ratio. However, the longest voltage vectors which configure the most outer region do not have the redundancy, even if the 1:0.5 ratio is employed.…”

“…In the normal operation of the dual inverter motor drive, both of the DC-bus battery voltages are same. However, once the failure occurs, the INV2 is operated with the capacitor and the capacitor voltage is controlled at half of the battery voltage of the INV1, in order to take advantage of the redundancy in the switching states [19]. Therefore, it is required to discharge the capacitor voltage of the INV2 down to the command value, immediately after the failed battery of the INV2 is isolated with the relay.…”

Control Method that Reduces the High Harmonic in the Overmodulation Drive of the Dual Winding Motor during Voltage Supply Unbalance

“…The windings in the dual winding motor are connected to the inverters with the respective voltage supply. We have been motivated by the characteristic of the two voltage supply system in which the two systems are electrically independent unlike the open winding motor drive system with two voltage supplies (13) , we studied overmodulation in the two voltage supply system (14) . In this paper, our former work is revised, and improved control is proposed.…”

Reduction of Voltage Harmonics in an Open-End Winding Induction Motor Driven by a Dual-Inverter with a Floating Capacitor in a Partial-Load Condition

“…Dual-inverter fed open-end winding (OEW) motor topologies and their modulation strategies have been researched for several purposes such as multilevel operations (5)- (8) , wide speed range operations (9)- (11) , fault-tolerant functions (12)- (13) . In particular, the dual-inverter topology, which has a single power supply and a floating capacitor in each inverter, can generate a five-level waveform in the winding phase voltage by keeping each DC-link voltage in a ratio of 2:1 (7)- (8) .…”